Security markers for determining composition of a medium

ABSTRACT

A method of determining a component of a medium comprises illuminating the medium to excite a marker associated with the component. Detected photoluminescent emission from the marker in response to the excitation is compared with one or more emission profiles. The component is identified based on a match between the detected photoluminescent emission and at least one of the emission profiles.

This application is a continuation-in-part of application Ser. No.11/016,658, filed Dec. 17, 2004, which is a continuation-in-part ofapplication Ser. No. 10/822,582, filed Apr. 12, 2004, now U.S. Pat. No.7,129,506.

The present invention relates to security markers which are difficult tocounterfeit. The security markers are generally attached to, or embeddedin, objects. The security markers provide indicia which can identifytheir origin and thus the origin of the object.

BACKGROUND OF THE INVENTION

Security markers are used to authenticate items. For example, bank notestypically include security markers such as watermarks, security threads,holograms, kinegrams, and such like. Chemical and biochemical taggantsare also used as security markers for items. However, in many cases suchtaggants must be removed from the item for authentication analysis. Thisis both time-consuming and expensive.

Optically based approaches, such as those using luminescent or, morecommonly, simple fluorescent inks and dyes, are also used toauthenticate items. Fluorescent inks and dyes emit light when excited byradiation of a particular wavelength. Information embedded in an itemusing fluorescent inks and dyes can be retrieved when the embedded markis illuminated with radiation of an appropriate wavelength.

An example of a particular type of fluorescent ink is described in U.S.Pat. No. 5,256,193, which is hereby incorporated by reference. Thefollowing patents describe various security labeling and printingapplications, and are hereby also incorporated by reference: JP 8208976;U.S. Pat. No. 4,736,425; U.S. Pat. No. 5,837,042; U.S. Pat. No.3,473,027; U.S. Pat. No. 5,599,578; GB 2,258,659; U.S. Pat. No.6,344,261; and U.S. Pat. No. 4,047,033.

Known fluorescent inks and dyes have the disadvantage that they havevery broad emissions spectra, which limits the number of different dyesthat can be used. For example, one ink may produce a color which spansfrom red through green in the visible spectrum. Another may produce acolor which spans from green through violet. Thus, if these two inks areused in or on an item, it is difficult to use a third ink with them,because the first two inks cover the entire visible spectrum.

For many purposes it is, therefore, desirable to provide securitymarkers having an emission spectrum comprising one or more narrow peaks.Similarly, it is desirable to provide security markers which areinexpensive to manufacture and incorporate in materials, difficult tocounterfeit, and quick and easy to detect in situ.

SUMMARY OF THE INVENTION

In one form, a glass composition is fabricated, which produces a uniqueluminescent signature in response to excitation, and the glasscomposition is difficult to copy to form a second composition whichproduces the same unique luminescent signature. More particularly, theglass composition produces a unique photoluminescent (PL) signature inresponse to excitation, and the glass composition is difficult to copyto form a second composition which produces the same unique PLsignature.

As used herein, a luminescent signature refers to aspects of luminescentemission from a security marker or group of markers that are unique tothat marker or group of markers. Similarly, a PL signature refers toaspects of PL emission from a security marker or group of markers thatare unique to that marker or group of markers. These aspects may includeone or more of: presence or absence of emission at one or morewavelengths; presence or absence of a peak in emission at one or morewavelengths; the number of emission peaks within all or a portion of theelectromagnetic spectrum comprising, for example, ultraviolet radiationto infrared radiation (e.g., approximately 10 nm to 1 mm); rate ofchange of emission versus wavelength, and additional derivativesthereof; rate of change of emission versus time, and additionalderivatives thereof; absolute or relative intensity of emission at oneor more wavelengths; presence or absence of regions of theelectromagnetic spectrum, for example ultraviolet radiation to infraredradiation, in which emission is above a predetermined absolute orrelative intensity; presence or absence of regions of theelectromagnetic spectrum, for example ultraviolet radiation to infraredradiation, in which emission is below a predetermined absolute orrelative intensity; ratio of an intensity of one emission peak to anintensity of another emission peak or other emission peaks; the shape ofan emission peak; the width of an emission peak; or such like.

According to a first aspect there is provided an optically detectablesecurity marker for emitting light at a predetermined wavelength, themarker comprising: a rare earth dopant and a carrier incorporating therare earth dopant, the interaction of the carrier and the dopant beingsuch as to provide a PL signature or response that is different fromthat of the rare earth dopant. As will be appreciated by those ofordinary skill in the art, the term “light” is not restricted to photonsin the visible spectrum, but includes photons in the ultraviolet andinfrared ranges.

A rare earth dopant comprising one or more rare earth elements has anintrinsic set of electronic energy levels. The interaction between thecarrier and the dopant is such that these intrinsic energy levels changewhen the dopant is incorporated into the carrier. For example, when thedopant is incorporated into a glass, new energy levels (from the glass)are made available for transitions, thus altering the electronarrangement, and hence the energy levels for photon absorption andemission (i.e. photoluminescence). These transitions can assistrecombinations that were previously prohibited. Altering the rare earthdopant, dopant chelate and/or the composition and/or structure of thecarrier changes these energy levels and hence the observed PL signature.

By virtue of this aspect an optically detectable security marker isprovided that can be tailored to have strong PL light emission at apredetermined wavelength when illuminated with a particular wavelengthof light. This enables a validator to validate the security marker bydetecting emission at the predetermined wavelength in response toradiation at the particular wavelength. Such a security marker is verydifficult to replicate by a counterfeiter.

The rare earth dopant may be a lanthanide or a compound comprising alanthanide.

The carrier may comprise a glass or a plastic. The carrier in which therare earth dopant is embedded may readily be produced in a variety offormats, e.g. spheres, beads, threads or fibers, suitable for inclusionin a variety of products such as those made from paper, plastic, wovenand non-woven textiles, and various composite materials, among others.Alternatively, the rare earth dopant may be an integral part of thesubstrate or matrix forming the underlying product.

A carrier incorporating one or more rare earth dopants producesnarrowband emissions in response to excitation. Due to these narrowemission bands, multiple carriers can be used (or a single carrier canincorporate multiple rare earth dopants), each prepared to have adifferent PL signature so that, for example, luminescence peaks atmultiple emission wavelengths can be provided in a single item withoutthe different peaks overlapping each other. This enables a securitymarker to be provided that has a PL signature selected from a largenumber of permutations, thereby greatly increasing the difficulty incounterfeiting such a security marker.

A carrier incorporating one or more rare earth dopants has a new energylevel profile that allows transitions different from those allowed byeither the rare earth dopant or the undoped carrier. The new energylevel profile results from the unfilled 4f electron shell in the rareearth ions, which allow f-f electron transitions. The new energy levelprofile allows atomic luminescence having a narrow peak rather thanmolecular luminescence that has a broad peak. The new energy levelprofile is particularly advantageous for security purposes because itprovides narrow emissions at wavelengths not naturally found in eitherthe rare earth dopant or the undoped carrier. These narrow emissions canbe used as part of a security marker.

A plurality of different rare earth dopants may be used. One or more ofthese different rare earth dopants may have intrinsic PL emissions thatare visible to the unaided human eye, for example in the range of390-700 nm. Similarly, one or more of these different rare earth dopantsmay have intrinsic PL emissions that are invisible to the unaided humaneye, for example in the infrared or ultraviolet range. Likewise, thecombined effect of the carrier and the rare earth dopant may be such asto cause the security marker to have PL emissions that are visible tothe unaided eye, or that are invisible to the unaided human eye.

The security marker may be excited by highly selective, high intensityvisible light and the resultant emission may be in the visible region orin the infrared region.

It may be desirable to add secondary dopants incorporating, for example,other rare earth elements to a carrier including primary dopants (i.e.,those dopants that have already been introduced into the carrier toproduce PL emissions at the predetermined wavelength) even though theemissions from these secondary dopants are not conducive to the desiredtransitions (i.e., PL emissions at the predetermined wavelength). Thisis because the energy levels of these secondary dopants can contributeto otherwise prohibited transitions. Thus, while the secondary dopantsmay not produce PL emissions at the predetermined wavelength, theycontribute indirectly by strengthening the PL emissions from primarydopants at the predetermined wavelength.

Various ratios and concentrations of dopants have been tested. In oneexample, the dopant comprised approximately 3 mol %, based upon thetotal number of moles in the composition. Approximately 1 to 3 mol % hasalso been tested for single and multi doped beads of glass (i.e., 1 mol% Eu, 1 mol % Tb, 1 mol % Dy for 1 bead in steps (of each) of 0.5 mol %up to 3 mol % Eu, 3 mol % Tb and 3 mol % Dy). Bead size wasapproximately 50 micron. One type of glass used has a soft point ofabout 740 degrees Celsius. The exact melting point depends on thespecific glass used, and may vary from 700 degrees Celsius to 1500degrees Celsius. For some embodiments, efficiency may level off fordoping above 3 mol %.

Different methods of doping glass with rare earth elements are known.The following patents or published applications describe various dopingmethods, and are hereby incorporated by reference: U.S. Pat. No.6,153,339; U.S. Pat. No. 5,262,365; and US Published Application2004/0212302.

Glass beads have been fabricated and tested (PL spectra has beenmeasured) for beads varying from 5 μm in diameter to 100 μm in diameter.Beads having a particular size can be specifically produced or passedthrough a sieve having appropriate apertures/reticulations.

According to a second aspect of the present invention there is providedan item having an optically detectable security feature for emittinglight at a predetermined wavelength, the security feature comprising: arare earth dopant and a carrier incorporating the rare earth dopant, theinteraction of the carrier and the dopant being such as to provide a PLsignature or response that is different from that of the rare earthdopant.

The item may be validated by illuminating the security feature at one ormore wavelengths and detecting emissions at the predeterminedwavelength.

The item may be a fluid. Examples of fluids particularly suitable foruse with the invention include fuel, paint, ink and such like.

The item may be a laminar media item. The laminar media item may be inthe form of a web, a sheet, and such like. Examples of sheet formlaminar media items include banknotes and financial instruments such aschecks, giros, and money orders.

The item may include a plurality of security features, each emittinglight at a different predetermined wavelength. Alternatively, anindividual security feature may include a plurality of rare earthdopants.

In one embodiment, an item may include a plurality of security featureseach having different concentrations of dopant, so that intensities ofthe predetermined wavelength emissions are different. By virtue of thisaspect, the relative emission intensity of different predeterminedwavelengths can be used as an additional layer of security for an item.For example, intensity of one predetermined wavelength may be 100,intensity of another predetermined wavelength 50, intensity of a thirdpredetermined wavelength 25, and intensity of a fourth predeterminedwavelength 50. More or less than four wavelengths can be used. Thisprovides a large variety of security profiles, where each profilecomprises PL emission at a plurality of predetermined wavelengths and aratio of intensities at the plurality of wavelengths. This makescounterfeiting even more difficult, as the quantities of each dopantmust be accurately replicated, in addition to the carrier energydifference.

In another embodiment, the PL emission from each security feature decaysover a different time period. By virtue of this aspect, the time overwhich emission occurs at a particular wavelength can also be used aspart of a security profile.

According to a third aspect there is provided a system for validating anitem having an optically detectable security feature emitting light atone or more predetermined wavelengths, where the security featurecomprises a carrier incorporating a rare earth dopant, the systemcomprising: means for illuminating the security feature with one or morewavelengths for producing emissions from the security feature; means fordetecting emission from the security feature at at least one of the oneor more predetermined wavelengths; means for filtering and comparing thedetected emission with a security profile for the item; and means forindicating a successful validation in the event of the emission matchingthe security profile.

The means for illuminating the item may comprise a pulsed light emittingdiode, a laser diode, or a broadband light source and, optionally, anillumination filter for ensuring that only a narrow band of wavelengthsilluminate the item.

The means for detecting emission may comprise a detection filter tofilter out all wavelengths except the predetermined wavelength, and aphotodiode to detect the intensity of light passing through thedetection filter.

In one embodiment, the illumination means comprises an array of LEDs,each LED having a different illumination filter, so that the item to bevalidated is illuminated with multiple narrow band wavelengths. In suchan embodiment, the detection means comprises an array of photodiodes,each photodiode having a different detection filter, so that theemission at each corresponding, predetermined wavelength can bedetermined.

According to a fourth aspect there is provided a method of validating anitem having an optically detectable security feature comprising acarrier incorporating a rare earth dopant emitting light at one of aplurality of predetermined wavelengths, the method comprising the stepsof: illuminating the security feature with light at one or morewavelengths; detecting emission from the security feature at apredetermined wavelength; filtering and comparing the detected emissionwith a security profile for the item; and indicating a successfulvalidation in the event of the emission matching the security profile.

According to a fifth aspect there is provided an optically detectablesecurity marker for emitting light at a predetermined wavelength, themarker comprising: a rare earth dopant incorporated within a carriermaterial, the dopant and the carrier material being such as to causeemission of visible light in response to excitation by visible light ofa predetermined wavelength.

The interaction of the carrier and the dopant may be such as to providea PL signature or response that is different from that of the rare earthdopant.

According to a sixth aspect there is provided a security item thatincludes an optically detectable security marker for emitting light atone or more predetermined wavelengths, the marker comprising: a rareearth dopant incorporated within a carrier material, the dopant and thecarrier material being such as to cause emission of visible light inresponse to excitation by visible light.

The security item may be a fluid, for example fuel, paint, ink and suchlike. Alternatively the security item may be a laminar media item, forexample banknotes and financial instruments such as checks.

The security item may include a plurality of security markers, eachmarker emitting light at one or more different predeterminedwavelengths.

According to a seventh aspect there is provided a security markercomprising a glass, such as a borosilicate based glass, or a plastic,and a rare earth dopant. The glass may include SiO₂; Na₂O; CaO; MgO;Al₂O₃; FeO and/or F₂O₃; K₂O, and B₂O₃, and the rare earth dopant maycomprise a lanthanide. The glass may have a composition of: SiO₂ 51.79wt %; Na₂O 9.79 wt %; CaO 7.00 wt %; MgO 2.36 wt %; Al₂O₃ 0.29 wt %;FeO, Fe₂O₃ 0.14 wt %; K₂O 0.07 wt %, and B₂O₃ 28.56 wt %, not precludingthe use of other glass mixes. The security marker comprising the glassand the rare earth dopant may be formed into micro-beads.

The security marker may further comprise a carrier, such as glass orplastic including one or more types of rare earth dopant. Theinteraction of the glass or plastic and the dopant may be such that thePL signature or response of the marker is different from that of therare earth dopant or the carrier. In particular, the interaction betweenthe carrier and the dopant may be such that the intrinsic energy levelsof the dopant change when it is incorporated into the carrier. Forexample, when the dopant is incorporated into a glass, new bonds areformed in the doped glass, thus altering the electron arrangement andhence the energy levels of absorption and PL emission. Altering the rareearth dopant, dopant chelate and/or the composition and/or structure ofthe carrier changes these energy levels and hence the observed PLsignature. A currently preferred dopant is any of the lanthanides exceptLanthanum.

The rare earth doped glass may be formed into micro-beads that can beincluded in, for example, a fluid such as ink.

According to an eighth aspect there is provided a kit comprising a) acollection of samples derived from a single batch of material comprisinga rare earth dopant and a carrier, all of the collection of samplesproducing a common PL signature when illuminated by a set of excitationfrequencies, and b) a scanner for illuminating a test sample with theset of excitation frequencies and ascertaining whether the test sampleproduces the PL signature.

The scanner may include data indicating the PL signature, and maycompare a PL signature obtained from the test sample with the data.

The scanner, using one of the collection of samples as a reference, mayobtain a PL signature from the reference, obtain a PL signature from thetest sample, and compare the two signatures.

As used herein, the word “dopant” refers to (i) additives (for examplerare earth elements) introduced to carrier components before the carrier(for example, glass) is produced, so that when the carrier is producedit contains the additives, which is referred to herein as a“pre-production dopant”; and/or (ii) additives introduced to the carrierafter the carrier is produced, so that the carrier is produced withoutthe additives present, which is referred to herein as a “post-productiondopant”. Thus, the term dopant covers additives introduced before(pre-production) or after (post-production) the carrier is produced.

Several methods for doping standard glass compositions with selectedrare earth dopants can be employed. In one method, test samples of dopedglass are prepared by the incorporation of the rare earth dopants intothe pre-production batch composition using the appropriate metal salt.The glass is prepared by heating the batch in a platinum crucible toabove the melting point of the mixture. In another method, existing,post-production standard glass samples are powdered and mixed withsolvent solutions of the rare earth dopants. The glass is then liftedout of the solvent, washed and oven dried.

An example of a glass that could be used as the carrier material for therare earth dopants is a borosilicate based glass. In particular, a glassthat could be used is as follows: Si_(O) ₂ 51.79 wt %; Na₂O 9.79 wt %;CaO 7.00 wt %; MgO 2.36 wt %; Al₂O₃ 0.29 wt %; FeO, Fe₂O₃ 0.14 wt %; K₂O0.07 wt %, and B₂O₃ 28.56 wt %. This can be made by ball milling sodalime beads for 5 minutes to create a powder to help melting and mixing.Then 5 g of the milled soda lime beads, 2 g of the B₂O₃ and 3 mol % ofthe rare earth dopant, for example Europium, Dysprosium and Terbium butalso others, are ball milled together for, for example, 3 minutes. Theresulting powder is then put in a furnace and heated up to 550° C. It isleft in the furnace at this temperature for about 30 minutes, to ensurethat the boric oxide is completely melted. Then the temperature isincreased to 1100° C. for 1 hour to produce a homogeneous melt. Thetemperature is increased again to 1250° C. and the molten glass ispoured into a brass mold, which is at room temperature, which quenchesthe glass to form a transparent, bubble free borosilicate glass, dopedwith rare earth ions.

The peak emission wavelength for PL emission of a security markercomprising a glass carrier incorporating a rare earth dopant depends onthe energy levels of the final rare earth doped glass. Altering theweight percentage of the network modifier oxides within the glass matrixwill change these levels and hence change the observed peak wavelength.Hence, to observe the correct PL signature, the glass composition has tobe known. Likewise, where two or more rare earth dopants are used in asingle carrier, varying the ratios, by mole percentage, of the dopantschanges the emission intensity at a given wavelength. Peak intensitiescan be used as part of an encoding scheme and so by varying the dopantlevels, there is provided an opportunity to provide even more encodingoptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates manufacture of a security marker in the form of arare earth doped glass billet having a unique PL signature according toone embodiment of the invention.

FIG. 2 illustrates the response of a particular rare earth doped glassbillet to excitation radiation.

FIG. 3 illustrates a general principle that an excitation frequency willproduce at least one emitted, or response, frequency.

FIG. 4 illustrates decay over time of the response frequency of FIG. 3.

FIG. 5 illustrates a time delay between excitation and response.

FIG. 6 illustrates sequential excitation by four excitation frequencies.

FIG. 7 illustrates part of a database for storing glass billetexcitation and response information.

FIG. 8 illustrates a prior-art table of energy levels of various dopantsin silicon.

FIG. 9 illustrates a computer storing a database comprising glass billetinformation which is accessible by a remote computer.

FIG. 10 illustrates one form of the invention, implemented in connectionwith a photocopier.

FIG. 11 illustrates a liquid carrier in which is suspended glassparticles of the type described herein.

FIG. 12 illustrates a coating on an article, which coating containsglass particles.

FIG. 12 a illustrates a complex product in the form of an automobileincluding a coating containing glass particles.

FIG. 12 b illustrates a complex product in the form of an ATM comprisingan improved module security system.

FIG. 13 illustrates a carrier supporting a glass particle.

FIG. 14 illustrates a carrier on which glass particles can representdata.

FIG. 15 illustrates a kit.

FIG. 16 illustrates a scanner.

FIG. 17 is a block diagram of a sensor arrangement.

FIG. 18 is a table showing various excitation wavelengths andcorresponding emission wavelengths and intensities for a Europium dopantin a borosilicate based glass.

FIG. 19 is a table showing various excitation wavelengths andcorresponding emission wavelengths and intensities for a Europium dopantin aqueous solution.

FIG. 20 illustrates a person accessing a physical space using an itemincorporating glass particles.

FIG. 21 illustrates a person accessing logical stores of a personalcomputer using an item incorporating glass particles.

FIG. 22 illustrates a gun operable when presented with glass particleshaving a predetermined luminescence.

FIG. 23 illustrates a system for reducing receipt fraud.

FIG. 24 illustrates two pharmaceuticals, each marked with a differenttype of glass particle, a luminescence spectrum from each of thedifferent types of glass particles, and identifying informationassociated with each luminescence spectrum.

FIG. 25 illustrates a reader for use with the pharmaceuticals of FIG.24.

FIG. 26 illustrates fuel tagged with glass particles leaking from anunderground tank and identifying source of the leak by detecting theglass particles.

FIG. 27 illustrates a system for determining a component of a medium.

FIG. 28 illustrates a mixture of two fluids incorporating glassparticles.

FIG. 29 illustrates photoluminescent signatures of the two fluids andresultant mixture of FIG. 28.

FIG. 30 a illustrates an item incorporating a different type of glassparticle at each of five layers of the item.

FIG. 30 b illustrates the item of FIG. 30 a after an outermost of thefive layers has been uniformly worn away.

FIG. 31 illustrates uneven wear of an item incorporating a differenttype of glass particle in each of two layers of the item.

FIG. 32 illustrates a power tool marked by spraying with a fluidincorporating glass particles.

FIG. 33 illustrates a sidewalk incorporating glass particles, and ablind person holding a walking stick that detects the glass particles.

FIG. 34 illustrates a road surface incorporating glass particles, and avehicle that detects the glass particles while the vehicle is movingalong the road surface.

DETAILED DESCRIPTION OF THE INVENTION

Reference is first made to FIG. 1, which illustrates processing steps toproduce a security marker according to one embodiment of the presentinvention.

Block 1 in FIG. 1 illustrates a collection of two types of rawmaterials: (1) a group of oxides and (2) one or more rare earthelements. The labels W, such as W1, indicate that each raw material ispresent in a specific weight. Thus, the collective labels W1-W10indicate a specific composition, by weight, of the raw materials.

Once combined, the raw materials are heated, cooled, and may be subjectto heat treatment including, optionally, annealing, as indicated by thearrow labeled PROCESS, to produce a glass billet 2. The glass billet 2is then cut into dice, pulverized into a powder, or otherwise processedinto any other desirable shape or size, as indicated by the arrowlabeled DICE/PULVERIZE/ETC. For example, the glass billet 2 can bebroken down into many small pieces alternately and interchangeablyreferred to herein as glass fragments or particles, and the like, whichcan be used as security markers.

The dashed arrow points to a block 3 which represents one of the dice, acollection of the powder, or another desirable form prepared from theglass billet 2. In the general case, when the block 3 is excited byradiation, indicated by frequencies F1 through F5, the block 3 will emitspecific frequencies, indicated by frequencies F6 through F10.

The specific emitted frequencies, and also the properties of thoseemitted frequencies, are unique to the specific glass billet 2 fromwhich the block 3 is derived. The properties of the emitted frequenciesare described in detail below, but include (1) intensity of each emittedfrequency and (2) decay rate of each emitted frequency.

In general, if the relative weights W are altered, different emittedfrequencies, with different properties, will be detected. Also, if theprocessing of the glass billet 2, including any annealing, is changed,then different emitted frequencies, with different properties, can alsobe detected, even if the elemental compositions of two billets 2 areidentical.

Therefore, in the general case, the emitted frequencies and theirproperties, obtained from a given set of excitation frequencies, dependon (1) the composition, that is, the relative weights W, and (2) theprocessing, including annealing (if any) of the glass billet 2.

FIG. 2 illustrates a generalized example of the response of a particularglass billet 2 to excitation radiation, and is based on FIG. 18, whichwill be described later. Graph 10 of FIG. 2 indicates the use of fourexcitation wavelengths, at 395, 415, 465, and 535 nanometers (nm) ofsimilar intensity. For the glass billet in question, the 535 nmexcitation produces one emitted wavelength 13 of indicated relativeintensity. The 465 nm excitation produces two emitted wavelengths 15 and17, of indicated intensities.

The 415 nm excitation also produces two emitted wavelengths 19 and 21,of indicated relative intensities. Finally, the 395 nm excitationproduces four emitted wavelengths 23, 25, 27, and 29, of indicatedrelative intensities. FIG. 18 sets forth the respective relativeintensities more precisely, in numerical form.

FIG. 3 illustrates a general principle that an excitation frequency F1will produce at least one emitted, or response, frequency F2. Responsefrequency F2 is characterized by an initial intensity I2, in this caseshown to be less than intensity I1 of excitation frequency F1. However,initial intensity I2 of response frequency F2 may be greater than orequal to intensity I1 of excitation frequency F1, depending upon, forexample, the composition and processing of the glass.

Also, as indicated in FIG. 4, intensity of response of frequency F2 maybe characterized by a decay time T2, which is, for example, the timerequired for the emitted intensity to decay to 50 percent of its initialvalue I2. However decay time T2 may be alternately defined as, forexample, the time required for the emitted intensity to decay to 25percent of its initial value I2, and the like.

In addition to the decay time T2, another time interval may be present,such as that shown in FIG. 5. As shown in FIG. 5, the response frequencyF2 may occur after a time interval DEL-T following excitation atfrequency F1. The delay time DEL-T may also be a property of the outputfrequency F2, and used to identify the glass billet.

In addition, the delay time DEL-T can be used to solve a particularproblem which can arise. As shown in FIG. 2, the excitation wavelengthof 395 nm produces luminescence peaks at four response wavelengths, oneof which 23 is at 535 nm. However, the luminescence peak at 535 nmcorresponds to an excitation wavelength of the same value. Thus, if thefour excitation wavelengths in graph 10 were applied simultaneously, aproblem could arise in determining whether a detected signal at awavelength of 535 nm was caused by the excitation at that wavelength, orby the response 23.

One solution to this problem is to utilize the time delay DEL-T of FIG.5. The excitation wavelengths are applied, removed (for example,de-activated), and then a detector is activated after DEL-T expires.This ensures that if a signal at wavelength 535 nm is detected, it isnot due to an excitation at that wavelength.

In addition, another solution to the problem would be to sequentiallyapply the excitations, as indicated by the sequence F1 through F4 inFIG. 6. When each excitation of a specific frequency is applied, adetector looks for a response, either at the same time, or after a delaysuch as DEL-T in FIG. 5.

The principles just described can be used to construct a database 30 asshown in FIG. 7. The column labeled BILLET refers to a specific billet,which contains a specific set of relative percentages of components, andwhich was subjected to specific processing. Processing refers to thetime-temperature history of the billet in melting and fusing the oxidesand the rare earth element(s) together, and includes any heat treatment,such as annealing.

The column labeled EXCITATION refers to the frequency of excitationapplied to the billet, or portion of the billet. In the case of BILLET1, two excitation frequencies F1 and F4 are indicated.

The column labeled RESPONSE refers to the frequency, decay time, andinitial intensity of signals emitted in response to the excitationfrequency. For example, in the case of BILLET 1, the excitationfrequency F1 produces emitted light of frequency F2, initial intensityI2, and decay time T2, and also emitted light of frequency F3, initialintensity I3, and decay time T3.

In addition, excitation frequency F4 produces emitted light from BILLET1 of frequency F5, initial intensity I5, and decay time T5.

Of course, the specific definitions of intensities, such as I5, anddecay time, such as T5, are here chosen for convenience. Otherdefinitions are possible, and values other than initial intensity and50-percent-decay-time can be used.

Also, if a delay time, such as DEL-T in FIG. 5, is found significant fora particular billet and excitation frequency, that delay time can alsobe included in the database, among other information.

As previously discussed, a PL signature refers to aspects of PL emissionfrom a security marker or group of security markers that are unique tothat marker or group of markers. As such, a PL signature can be definedas the response of a billet, or part thereof, to excitation at one ormore excitation frequencies, such as presence or absence of one or moreemitted frequencies, and/or one or more individual properties of theemitted frequencies such as absolute or relative intensity and decaytime. Such a PL signature can be used to, for instance, identify thebillet, or part thereof.

In one example, a PL signature is derived using normalized PL emissionfrom glass particles. In this example, the glass particles areilluminated (excited) and the resulting PL emission spectra comprisingemission intensity at one or more emission frequencies is measured. Tonormalize the measured PL emission spectra, the measured emissionintensity at a predetermined frequency is used as a reference by whichthe intensity at all other frequencies of interest in the PL emissionspectra will be scaled. In other words, the measured intensity of thosefrequencies of interest in the PL emission spectra, which may be all ofthe frequencies measured, or a sub-set thereof, will be scaled relativeto the measured intensity at the predetermined frequency.

Subsequently, the scaled emission intensity at each frequency ofinterest is translated into a data block comprising a predeterminednumber of bits. As an example, if there are eight frequencies ofinterest, then eight data blocks are produced, each having apredetermined number of bits. Translation of the scaled intensities mayuse digitization error correction, such as parity bits, to take accountof boundary problems. This ensures that a given intensity willconsistently translate to the same data block value even if theintensity varies by a relatively small amount (such as five percent)when measured at different times, and/or under different conditions andsuch like.

The individual data blocks are then concatenated to produce a continuoussequence of data blocks for further use. This continuous sequence ofdata blocks can, for example, be used by itself as a PL signature forthe illuminated glass particles, or it can be used to form part of amore complex PL signature for the glass particles.

If a more complex PL signature is desired, the decay of PL emissionversus time may also be used to derive a PL signature. The decay of PLemission versus time may be obtained by, for example, measuring multiplePL emission spectra, each at a different time after de-activation of anillumination source, but before the PL emission from the glass particleshas decayed completely.

Deriving a single PL signature from multiple PL emission spectra may beachieved by concatenating the individual PL signatures derived for eachof the measured PL emission spectra as described in the example above.Likewise, the individual data blocks for each measured PL emissionspectra may be concatenated to form a single PL signature from themultiple PL spectra. Thus, if three PL emission spectra are measured,each having eight frequencies of interest, then a PL signature resultingfrom concatenation of the data blocks from the three comprisestwenty-four data blocks. To counterfeit this PL signature it would benecessary to provide a material that had, not only a PL emission havingthe same initial intensity ratios at the frequencies of interest, butalso having the same intensity decay characteristics at each of thefrequencies of interest.

Representing a PL signature as a sequence of bits allows a measured PLsignature to be matched with one or more pre-stored PL signatures veryquickly and easily using digital comparing techniques, for example, anexclusive nor (XNOR) Boolean function. Once matched, the PL signaturecan be validated, and/or additional information associated with thematched PL signature can be retrieved from a storage and presented to auser, and the like.

In other examples, additional methods of generating and representing aPL signature, such as representing the PL signature as a stored table ofrelative or absolute emission intensities and decay times at one or morefrequencies of interest resulting from various excitation frequencies,and such like, may be used.

For example, a PL signature of BILLET 1 in FIG. 7 can be defined as theresponse of BILLET 1 to excitation frequencies F1 and F4 as shown in thedashed box 33 of FIG. 7. Subsequently, a security marker can beidentified as being derived from BILLET 1 if the response of thesecurity marker to excitation frequencies F1 and F4 comprises the PLsignature of BILLET 1, namely the response shown in the dashed box 33.

Of course, a PL signature of BILLET 1 can also be defined by a sub-setof the contents of the dashed box 33, such as only intensity I2 anddecay time T2 of response frequency F2. Likewise, a PL signature ofBILLET 1 may include only response information relating to excitationfrequency F1. In such case, response information relating to excitationfrequency F4 could be eliminated and/or otherwise ignored in definingthe PL signature of BILLET 1, and in any subsequent attempt to identifyBILLET 1 or part thereof. In a similar fashion, response informationrelating to background excitation sources can be eliminated and/orexcluded from the PL signature of a billet.

It is also possible that a single billet may have more than one PLsignature. For example, referring to FIG. 7, a first PL signature ofBILLET 2 may be defined as the response of BILLET 2 to excitationfrequency F1, namely F6, T6, and 16. Likewise, a second PL signature ofBILLET 2 may be defined as the response of BILLET 2 to excitationfrequency F6, namely F7, T7 and I7. Either or both of the first andsecond PL signatures of BILLET 2 may then be used to, for instance,identify a security marker comprising BILLET 2 or any part thereof, suchas the pulverized glass powder or dice (etc.) of FIG. 1. Having morethan one PL signature for a BILLET is particularly advantageous becauseif a counterfeiter somehow managed to create a material that replicatedthe first PL signature of the BILLET, secure identification orvalidation of the BILLET (or a portion of the BILLET) could still beperformed using the second PL signature. For example, a first PLsignature is defined as a response of BILLET 2 to excitation at a firstexcitation frequency F1. A second PL signature may be defined as aresponse of BILLET 2 to excitation at a second, different excitationfrequency F6. In such case, it is highly unlikely that a counterfeitmaterial that replicates the first PL signature at the first excitationfrequency F1 will also replicate the second PL signature at the second,different excitation frequency F6.

Several significant features which distinguish the pulverized glass/dice3 (etc.) of FIG. 1 from prior art security markers or taggants are thefollowing.

One is that it is difficult to reverse-engineer the dice. That is, it isdifficult for one to excite the glass as indicated in FIG. 2, detect thePL signature, and then fabricate a glass which produces that PLsignature. One reason is that a complete database of the type shown inFIG. 7 is not known to exist. That is, a complete database which coversall possible compositions and processing steps of glass billets, andtheir PL signatures, is not known to be available in the literature.

This fact distinguishes the invention from systems which may appear tobe similar, but are not. For example, silicon, a crystal, can be dopedwith different elements. The doped silicon can then be excited, andradiated light of frequency corresponding to the doping element will bedetected. Based on the frequency of the emitted light, one can consultknown tables, and determine the identity of the dopant. FIG. 8illustrates such a table. The frequency of emitted light will depend onthe drop in energy D experienced by an electron, and that drop willdepend on the energy level E created by the dopant. One can thusreproduce the silicon-dopant system, based on the table.

However, to repeat, such tables are not known to exist for the glasstaggants of the present invention.

A second feature is that the glass taggants of the present invention arenot crystalline. Glasses, in general, are amorphous solids, they are notcrystals. Thus, an energy level system corresponding to that of FIG. 8is not present or, if present, is different for the different glassesdescribed herein.

A third feature is that some glasses are classified as refractorymaterials. Dice, or powders, of such glasses can withstand hightemperatures. Such glasses are unaffected by temperatures of 400, 500,700, 1000 degrees F., and higher. This distinguishes them from most, ifnot all, fluorescent inks and paints, and the surfaces to which the inksand paints are applied.

Several applications of the glasses under consideration will now bediscussed.

In FIG. 9, a database 50 is stored in a computer 55. The database 50 is,for example, generated by a glass foundry (not shown) which fabricated abillet 2 in FIG. 1 of glass. The glass foundry subjected the billet, orfragments of it, to various excitation frequencies, and measured the PLsignature of the glass. Data concerning the glass, such as thecomposition, processing steps including heat treatment such asannealing, excitation frequencies and resulting PL signatures, arestored in the database 50, and indicated by blocks D1-D8. The identityof the foundry can also be included in the data.

The glass foundry can repeat the process for another billet of glass, ofdifferent composition and/or process steps.

Subsequently, a user (not shown) would excite a sample 60 of the glassbillet to determine a PL signature. For example, the sample may beattached to a specific article (not shown). The user would applyexcitation frequencies to the sample 60, and obtain a PL signature ofthe sample 60. FIG. 2 illustrates generalized excitation frequencies inimage 10, and the PL signature which results.

The PL signature obtained can be represented as a collection of data.The data may be raw intensity versus wavelength and/or time data, aprocessed version of this raw data, a subset of this raw data, or suchlike. The user then transmits this collection of data to the computer 55in FIG. 9, over the INTERNET, using the user's own computer 65. Throughuse of database 50, knowledge of the PL signature allows one toascertain the billet of glass from which the sample 60 in FIG. 9originated, or any additional data associated with the billet in thedatabase, such as the identity of the foundry which fabricated theglass.

In addition, other information can be included in the database 50 inFIG. 9. For example, a billet having a given PL signature can betransferred to a specific party, such as a government. That party can beidentified in the database 50, in connection with the data regarding thebillet.

As a more specific example, fragments of the billet can be pulverizedand added to an ink which is used to print currency. If a sample 60 ofthe glass billet in the currency is excited, and the resultant PLsignature points to the specific billet, then it is known that thecurrency is associated with the billet delivered to the particulargovernment.

Thus, in general, a sample 60 in FIG. 9 of a billet can be used to tracethe origin of the sample. Or database 50 in FIG. 9 can indicate theoriginal owner of the billet from which the sample 60 is derived.

In another application, the glass can be used to suppress counterfeitingor copying. Block 100 in FIG. 10 represents a photocopier. Block 105represents a sheet to be copied, which can take the form of a visualimage on a paper carrier. Block 10 represents a fragment of the glassattached to the paper carrier.

Block 115 represents a detector, which illuminates the sheet 105 at thecopying station, and thereby illuminates block 10, the fragment ofglass. If block 10 produces a particular PL signature, then the detector115 blocks copying, so that the photocopier 100 will not copy the sheet105.

Alternately, the system could be designed so that only sheets bearing anauthorizing block 110 can be copied. Thus, if the proper PL signature isdetected, copying is allowed, and ordinary sheets lacking a block 110cannot be copied. Alternatively, or additionally, if the authorizingblock 110 has a first PL signature then the sheet can be copied for afirst fee; if the authorizing block 110 has a second PL signature(instead of—and different from—the first PL signature), the sheet can becopied for a second fee (higher than the first fee); whereas, if theauthorizing block 110 has a third PL signature (instead of—and differentfrom—the first or second PL signatures) then the sheet cannot be copied.This provides a hierarchy of permissions for photocopying, withassociated fees where photocopying is permissible, and may be linkeddirectly or indirectly to a copyright licensing organization forautomatically reporting and/or collecting licensing fees. Otherapplications that are similar to this will be evident to one of skill inthe art. For example, instead of a photocopier machine, a multi-mediacopier (such as a DVD copier or burner, or a CD copier or burner) mayhave a reader installed to permit copying of media items (DVDs, CDs, andsuch like) based on a PL signature of a fragment of glass incorporatedin the item to be copied.

In another application, fragments 150 of the glass in FIG. 11 are addedto a liquid carrier 155, such as a varnish, ink, lacquer, paint,adhesive, or such like. In one embodiment, the fragments take the formof a fine powder, and have no dimension larger than, for example, onemicron, five microns, ten microns, fifteen microns, or twenty microns.In one embodiment the powder is sufficiently fine that the granules areinvisible to the naked eye. In another embodiment, the grains of thepowder are approximately the size of the grains of common table salt. Ina convenient embodiment, each grain is in the form of an approximatelyfive micron diameter generally spherical bead.

The liquid carrier comprises a paint which is painted onto an article170 in FIG. 12, forming a coating 175. The PL signature of the particlescan be detected in the manner described above, and the database 50 inFIG. 9 can then be used to deduce information about the article 170based on the detected PL signature. The article 170 may be a complexproduct (having many separate parts), where each part is painted usingthe paint including the fragments 150. This ensures that the entireproduct has the same PL signature, even though the product is acomposite of many parts, as will now be described with reference to FIG.12 a.

FIG. 12 a shows in simplified block diagram form an automobile 171having six painted panels 172 a to 172 f and a chassis 173. The panels172 and the chassis 173 have the same PL signature because they arecovered by paint including the fragments 150. For clarity, theautomobile 172 is shown having only six panels; however, an automobilemay have many more panels than six. If parts from another automobile areused to replace the original panels 172 or chassis 173 (for example,because of damage caused by a road traffic accident) then the new partswill have a different PL signature. This allows potential buyers toascertain whether the automobile has been repaired by measuring the PLsignature from various parts of the automobile 171.

It will now be appreciated that this provides a powerful tool whichenables a buyer, or a person evaluating a complex product, to identifyany products that have been formed by combining two or more differentproducts. Those skilled in the art will now appreciate that the complexproduct may be any of a variety of products, such as airplanes,automated teller machines (ATMs), and such like.

Where complex products include a large number of parts that are replacedto maintain the product in working order, or to upgrade thefunctionality of the product, then authorized replacement parts mayinclude a unique PL signature that is automatically scanned by a readerin the complex product when they are installed. If the replacement partsdo not have the authorized PL signature then the product may notcommunicate information to, or may not allow operation of, theunauthorized part. This example has value in products such as ATMs whichhave many different modules that inter-communicate and that receive andtransmit sensitive information.

FIG. 12 b illustrates an ATM 180 embodying an improved module securitysystem. The ATM 180 has a plurality of modules 182, including a cardreader module 182 a, a cash dispenser module 182 b, and a receiptprinter module 182 c. The ATM 180 also has an ATM controller 184 thatcontrols the operation of the ATM 180 and the modules 182 therein.

The ATM controller 184 includes a light guide arrangement 185 thatprovides an optical link between the ATM controller 184 and each module182. The optical light guide arrangement 185 includes an optical coupler186 mounted to the ATM controller 184 in the vicinity of detector 187.The detector 187 includes an illumination source 187 a and a sensor 187b.

The optical coupler 186 includes a lens portion 188 for focusing (i)light from the illumination source 187 a into the optical coupler 186,and (ii) light from the optical coupler 186 into the sensor 187 b. Theoptical coupler 186 also includes an entry/exit port 189 for each module182 in the ATM 180 that is to be secured. A dedicated light pipe 190 foreach module conveys light between the module and its respectiveentry/exit port 189. Thus, the ATM controller 184 is coupled to the cardreader module 182 a by a card reader light pipe 190 a extending from thecard reader module 182 a to the card reader entry/exit port 189 a in theoptical coupler 186. Similarly, a light pipe 190 b couples the cashdispenser module 182 b to the cash dispenser entry/exit port 189 b; anda light pipe 190 c couples the receipt printer module 182 c to thereceipt printer entry/exit port 189 c.

Each light pipe 190 is coupled to a respective module 182 at an area onthe module that includes glass fragments having a PL signatureassociated with that module. For example, the card reader module 182 amay have a first PL signature, the cash dispenser module 182 b may havea second PL signature (different from the first PL signature), and thereceipt printer module 182 c may have a third PL signature (differentfrom the first PL signature and also different from the second PLsignature).

When a module 182 is replaced in the ATM 180, the ATM controller 180illuminates the new module 182 via the optical coupler 186 and lightpipe 190 for that module, and detects the PL signature from that module.If the PL signature does not match the PL signature expected for thatmodule then the ATM controller 180 may not communicate with that module,or may only provide minimal communications to that module, therebydisabling some or all operations of that module.

Significantly, in some cases, an article can perform a function, and thepresence or absence of glass particles does not interfere with thatfunction, such that the function can be performed whether or not theparticles are present. For instance, if the article is a handgun, thepresence or absence of glass particles in, for example, paint applied tothe handgun, does not interfere with the function of the handgun, andthe particles need not be present for that function to exist. However,in some examples, the particles may be used to permit or deny access toa function performed by the article, as in the case of a key to secure aphysical or electronic space.

As shown in FIG. 20, a physical space 600, such as, for example, a roomin a prison or in a nuclear weapons facility, may be secured by a door602 having a lock 604 controlled by a reader 606 that only allows entryto a person 608 presenting an item 610 incorporating the correctparticles.

The reader 606 comprises: an excitation source 612 in the form of a pairof LEDs to stimulate PL emission from the particles; a detector 614 inthe form of an array of photodiodes to measure PL emission from theparticles; a store 616 in the form of an EPROM for storing one or morepre-defined access profiles; and a processor 618. To access the room600, a person 608 presents the item 610 to the reader 606. The item maybe clothing (for example a shirt or gloves), a token (such as anidentification card), and such like. Upon presentation, the reader 606pulses the LEDs 612 to illuminate the item 610 at one or more excitationwavelengths, and detects PL emission from the item 610 in response tothe excitation using the detector 614. The processor 618 processes thedetected PL emission to generate an access signature. The processor 618then compares the access signature with the predefined access profilesstored in the EPROM 616, and if the access signature matches one of thepre-defined access profiles, then the processor 618 sends a signal toopen the lock 604 and allow access to the room 600.

In one embodiment, processing the detected emission to generate anaccess signature may comprise identifying one or more peak emissionwavelengths from the detected emission. Likewise, comparing the accesssignature to one or more pre-defined access profiles may comprisecomparing the identified peak emission wavelengths to respective peakemission wavelengths of the one or more pre-defined access profiles todetermine if a match is found.

In another embodiment, processing the detected emission to generate anaccess signature may comprise calculating one or more ratios ofintensity at one or more peak emission wavelengths found for thedetected emission. Comparing the access signature to one or morepre-defined access profiles may, then, comprise comparing the calculatedratios of intensity to respective ratios of intensity for the one ormore pre-defined access profiles to determine if a match is found.

In another embodiment, instead of the space being physical, it may beelectronic, such as a store on a personal computer, PDA, self-serviceterminal, server and the like. One such example is shown in FIG. 21. InFIG. 21 a personal computer 650 is shown having a processor 652electrically connected to RAM 654, and a hard disk 656 comprising aplurality of logical stores 658, shown as 658-1, 658-2, . . . , 658-n.Access to the logical stores 658 is controlled by an electronicgatekeeper 660 residing in RAM 654 and executed by the processor 652. Auser 662 of the computer 650 desiring access to one or more of thelogical stores 658 must present an item 664 such as a token or clothingincorporating one or more security markers 666 to a reader 668comprising a light source 670 and a detector 672. The reader 668 iselectrically coupled to the computer 650 by, for example, a USBconnection 674.

In use, the processor 652 sends a signal to the light source 670 in thereader 668 to illuminate the item 664, and receives a signal from thedetector 672 using USB connection 674. The received signal comprisesdetected emission from the one or more security markers 666 incorporatedin the item 664 resulting from the illumination. The detected emissionis then processed by the processor 652, and the resulting processedemission is compared to one or more access profiles 676 in RAM 654.Access profiles 676 define access rights to one ore more of the logicalstores 658. If a match is found between the processed emission and oneof the one or more access profiles 676, access to one or more logicalstores 658 is provided to the user 662 by the electronic gatekeeper 660according to the respective access rights.

In an alternate embodiment, the reader 668 additionally includes areader processor (not shown) for processing the detected emission,comparing the processed emission to one or more access profiles 676 in areader store (not shown), determining if a match exists, and sending asignal to the electronic gatekeeper 660 via USB connection 674 toauthorize access to one or more of the logical stores 658 by the user662 according to the matched access profile. In all cases, one or morematches may be found providing access to one or more of the logicalstores 658. In addition, in a further embodiment, the reader 668 may beincorporated within the personal computer 650.

A token to gain access to a secure area may take the form of a glass rodhaving security markers incorporated in it. The rod may have rings ofdifferent security markers, such that each ring has a unique securitymarker, the rings being spaced along the length of the rod. To gainaccess, the rod is lowered into a reader to a depth at which one or morerings can be read. Access is provided if the correct marker rings areread such that the correct PL signature is provided.

Further, an article may only perform a function in response to reading apredetermined PL signature. For example, a handgun may include a readerin a grip of the gun configured so that the gun will only fire a bulletwhen a user presents to the reader particles having the correctsignature. One such arrangement is shown in FIG. 22.

In FIG. 22, a gun 700 includes a reader 702 in the grip of the gun 700.The reader 702 comprises a light source 706, a detector 708, a memory710 and a solenoid 712, all of which are electrically coupled to acontroller 714 for controlling operation of the reader 702. Solenoid 712includes an inductive coil 716 surrounding a movable shaft 718. Thesolenoid 712 is located such that a hammer 720 of the gun 700 will notmove, and the gun 700 will not fire, when the movable shaft 718 is in afirst, extended position, and the hammer 720 will move, and the gun 700will fire, when the shaft 718 is in a second, retracted position.

In operation, a user (not shown) presents particles 722 to the reader702 via a glove 724 which incorporates the particles 722. Upon commandfrom the controller 714, the light source 706 illuminates the glove 724,and the detector 708 detects resulting emission from the particles 722in the glove 724. The controller 714 then processes the detectedemission and compares the processed emission to one or more operationprofiles in the memory 710. If a match is found, the controller 714sends a signal to the inductive coil 716 of the solenoid 712 to retractthe shaft 718, allowing firing of the gun 700. If no match is found, thecontroller 714 sends a signal to the inductive coil 716 of the solenoid714 to extend the shaft, disabling firing of the gun 700.

In other embodiments, the solenoid can be designed to normally extendthe shaft 718, disabling firing of the gun 700, until a retract signalis received from the controller 714. Further, in addition to the glove724, a user may present the particles 722 to the reader 702 in a varietyof alternative ways including holding the grip with a finger on whichthere is a ring including the particles 722, or holding the grip with afinger having a tattoo including ink incorporating the particles 722,and the like.

An extension of this is that a gun may not fire if a reader associatedwith the gun is pointed at a target that includes a security markerhaving a predetermined signature. This may be used to reduce so-called“friendly fire” by, for example, incorporating the particles into theuniform of a friendly soldier. It may also be used to ensure thatweapons falling into the hands of an enemy cannot be used by the enemyagainst the army who manufactured the weapon.

Although the example of a gun has been given, it will be appreciatedthat performance or activation of a function of other articles could becontrolled by such particles, for example, automobiles, industrialmachinery, power tools, boats, airplanes, electronics, computers,self-service terminals including ATMs, and such like. Further, wheremultiple functions are provided by an article, performance of one ormore of the multiple functions may be controlled by these particles.

In some applications, multiple people may each have to provide a tokento enable an item to operate. For example, to launch a missile (such asa nuclear weapon), two or more people may each have to provide a token,and each token may have a different PL signature.

In another application, it is not necessary to consult a database. Adetector, as described herein, can be equipped with data which indicatesa PL signature of fragments from a glass billet. Or the data canindicate multiple PL signatures, for multiple billets.

In use, an article 210 in FIG. 13, which carries a glass fragment 215,is submitted to a detector 220. The detector 220 obtains the signatureof the fragment 215 and, if the signature matches a stored signature,the detector thereby deduces information about the article 210. Suchinformation can relate to authenticity, origin, ownership (includingchain of custody), information about the article 210, or any othercharacteristic which possession of a fragment 215 having a predeterminedsignature can represent.

For example, the article 210 can take the form of a document (such as apassport, visa, customs sheet, will, stock certificate, certificate ofauthenticity, boarding pass, receipt, invoice, prescription, a standardform, an operator's license, driver's license, or such like), an item offine art, a label, a registration plate or card for a vehicle or otheritem commonly registered with a government, a written signature orfingerprint carried on a card, or a storage medium such as a CD, DVD, orfloppy disc. If the fragment 215 emits a specific PL signature, thenthat signature indicates that the article 210 may be copied, or isprohibited from being copied, as appropriate. The articles can also takethe form of a credit card, debit card, charge card, loyalty card,telephone card, stored value card, or casino chip. If the article is aform, it may include a URL, or some other link, encoded using thefragments, to allow a user to ascertain the source of the form or alocation to obtain new forms from.

Where the article is valuable merchandise, such as china or pottery, themanufacturer may mark “seconds” (that is, merchandise that has failed aquality inspection and is sold at a reduced price) or reconditionedarticles, with glass fragments emitting a specific PL signature uponexcitation so that the “seconds” (or reconditioned items) cannot be soldas perfect merchandise.

In another example, a person may have a personal pen charged with inkincluding glass fragments having a PL signature unique to that person.This pen allows the person's written signature to be validated, not onlyby comparing a written signature claimed to be written by the personwith the person's normal written signature, but also by ascertainingwhether the ink used includes glass fragments emitting the person'sunique PL signature upon excitation. The person may have personalizedwriting paper (such as letter-headed paper) that indicates what theunique PL signature is (for example, it may include an image of thespectrum corresponding to the PL signature; or a type-writtendescription of the PL signature, such as peaks at 500 nm, 515 nm, and530 nm). This would allow a recipient to verify the claimed writtensignature by comparing the PL signature read from the ink used in thewritten signature with the PL signature described on the personalizedwriting paper.

If the article 210 is a label, it may be attached to another item. Thelabel may be distributed throughout the item. For example, if the itemis an article of clothing, the label may incorporated within the fabricof the clothing so that if the clothing is worn or washed, then thelabel will be removed, at least in part, from the clothing. This allowsa merchant to determine if the clothing has been worn or washed. Thismay be advantageous for retailers who have a policy of not providingcustomers with refunds for clothing that has been worn or washed.

Security markers may also be used to store information, in a similar wayto how a CD stores information, except that the security markers becomethe bumps for encoding, thereby providing secure media.

Likewise, security markers may be used in retail locations to reducereceipt fraud. Receipt fraud occurs, for example, when a person buys anitem from a retailer, photocopies a receipt for that item, then goesback to the retailer, removes an identical item from the shelf, and“returns” the unpaid for item using the photocopied receipt. This fraudcan be perpetrated against a large retailer many times using photocopiesof a single receipt.

One example of how an embodiment of the present invention can overcomethis fraud is to provide receipts to retailers that include a uniquecode for each store. For example, a large retailer may have stores inevery major city in the U.S. However a Dayton, Ohio store has adifferent unique code to a Stowe, Vt. store owned by the same retailer.These codes are provided using security markers. In one example, thesecurity markers are applied to the receipt via a clear adhesive that isprinted on the master rolls of receipt paper together with otherprinting information (such as advertisements). This clear adhesive andthe security markers are invisible to human eye, so they function as acovert security feature. The master rolls of receipt paper are then cutinto individual rolls suitable for a point of sale station, and securelydistributed to the appropriate store for that code.

In another example, the security markers are applied at the point ofdelivery to the customer (that is, at the checkout station), either byprinting, pressure, or other convenient mechanism.

One example of a system for preventing receipt fraud is shown in FIG.23. The system of FIG. 23 includes a wireless reader 800, and a receipt802 incorporating one or more security markers 804. The wireless reader800 includes a light source 806 for illuminating the receipt 802 andexciting the security markers 804, a detector 808 for detectingresultant emission from the security markers 804 in response to theexcitation, a wireless communication module 810 for communicating with aserver such as a point-of-service terminal (not shown), one or morebatteries 812 for providing power to the various components of thewireless reader 800, and a controller 814 for controlling operation ofthe wireless reader 800. The controller 814 comprises a processor 816and a memory 818 storing one or more valid PL signatures 820. Thewireless reader 800 further includes a proximity sensor 822 for sensingproximity of an object such as the receipt 802, and thereby causing thereader 800 to attempt to read the security markers incorporated into thereceipt 802.

Upon presentation of the receipt 802 to the reader 800, the proximitysensor 822 signals the controller 814 to initiate a read operation. Thecontroller 814 then sends a signal to the light source 806 to illuminatethe receipt 802 to excite the security markers 804. The detector 808then detects emission from the security markers 804 resulting from theillumination, and sends the detected emission to the controller 814,where it is processed by the processor 816 to ascertain a PL signatureof the detected emission. The processor 816 then compares theascertained PL signature of the detected emission to the one or morevalid PL signatures 820 in the memory 818 to determine if a match isfound. If a match is found, the receipt 802 is found to be valid and anitem whose purchase is indicated by the receipt 802 may be returned. Ifno match is found, the receipt 802 is found to be invalid, and no returnmay be made.

Valid PL signatures 820 are downloaded to the reader 800 on anon-demand, or scheduled, periodic basis from a server (not shown) usingwireless communication module 810. Likewise, in other embodiments,processed or raw, detected emission data can be uploaded from the reader800 to a server (not shown) using wireless communication module 810 forprocessing and/or comparison by the server against valid PL signaturesstored in an on-line database accessible to the server. Further, inother embodiments, a user operable switch (not shown) can be used toactivate the reader 800 in addition to, or rather than, the proximitysensor 822.

In the event there is no, or no matching PL signature then the receiptshould be investigated as a potential photocopy, and may be part of afraud. Further, if a valid PL signature is present, then it can bechecked against the PL signature for the store that issued the receipt(which is printed on the receipt). If the two PL signatures do not matchthen the receipt may be a photocopy printed onto a stolen roll ofreceipt paper.

As another example, since differing billets of glass produce differentPL signatures, those signatures, or the corresponding billets, can actas identification numbers. These ID-glasses can be attached to, orembedded in, articles to indicate ownership. This concept is applicableto articles such as items of fine art, precious metals and jewelry,human tissues such as organs, semen, and blood, and certificates.

As a specific example, an ID-glass can be inserted into a body fluidwhich is to be tested for illness, or presence of drugs or alcohol. TheID-glass, being inert to most common reagents, will not affect the testresults, except perhaps by contaminating an optical test, which would berare. The ID-glass identifies the owner of the fluid.

As another example, an ID-glass can identify origin of an article, andthus provide authentication. As a specific example, this can apply toitems of fine art, liquors, perfumes, human tissues, admission tickets,and entertainment recordings such as video and audio tapes and discs.

As another example, the ID-number feature of the ID-glass can be used toclassify articles or substances. As a specific example, ten differentID-glasses, with ten different PL signatures, can be fabricated. Thesecan be used to distinguish ten ostensibly identical, yet different,articles. For example, while contact lenses may look identical, theirinherent prescription may be different. A tiny ID-glass included on theedge can identify the contact lens. A similar principle applies to bloodtype, pharmaceuticals, chemicals, and so on.

Pharmaceuticals can be distinguished by including a taggant with aunique PL signature on or in a medication. The taggant may comprise oneor more fragments of a single type of rare earth doped glass, or one ormore fragments of multiple types of rare earth doped glass. The taggantmay be located on or in each individual medication or pill, and/on or ina package containing the medication or pill, and such like. For example,as shown in FIG. 24, one or more rare earth doped glass fragments 840and 842 with unique PL signatures 844 and 846 may be incorporated in theouter coating of medications 848 and 850, respectively.

The PL signatures 844 and 846 may be associated with identifyinginformation such as medication type, trade name, active ingredient,manufacturer, strength, dose, dose frequency, adverse interactions, andthe like, which may be provided to a user through, for example, a screen852 and 854 of a reader (not shown) adapted to ascertain the respectivePL signatures and access and present the identifying information. Suchuse would make it simple to distinguish between, for example, ananalgesic and a medication that reduces blood clots. Likewise, it wouldallow automated medicine dispensers to distinguish reliably betweendifferent types or strengths of medication. Similarly, such use couldinhibit or prohibit dispensing two or more medications havingpotentially adverse interactions by providing appropriate indication ofthe same to a user or an automated dispense system.

As shown in FIG. 25, an appropriate reader 860 for pharmaceutical usemay comprise an illumination source 862, a detector 864, a processor866, a memory 868, a battery 870, a switch 872, a display 874 and aspeaker 876. In use, the reader 860 is activated via the switch 872.After activation, the illumination source 862 illuminates a medication,such as medication 848, at one or more illumination wavelengths 878.Upon illumination and/or at some defined time thereafter, the detector864 detects emission at one or more emission wavelengths 880. Theillumination and emission wavelengths, 878 and 880, respectively, areassociated with PL signatures of glass fragments for which the reader860 is configured and/or programmed to read such as PL signatures 844and 846 of FIG. 24. Subsequently, the processor 866 compares thedetected emission with one or more emission profiles 882 stored in thememory 868. If a match is found, desired, associated identifyinginformation 884 is retrieved from the memory 868 and provided to theuser via the display 874. If no match is found, this result is alsoindicated on the display 874. The result of a match, as well as anon-match, may further be indicated via one or more audible tonesthrough the use of the speaker 876. In one embodiment, a single, highpitch tone may be used to indicate a successful read, while a single,lower pitch tone may be used to indicate an unsuccessful read. Othercombinations of number, frequency, and duration of tone may also beused.

In one embodiment, the reader 860 may be programmed or adapted toidentify a single medication 848. In a further embodiment, the reader860 may be programmed or adapted to identify a range of medicationstaken by a single individual or provided by, for example, a single or arange of manufacturers, and the like. Likewise, the reader 860 may alsobe programmed or adapted to indicate adverse interactions, and provide awarning to a user to avoid taking, or seek proper medical attentionbefore taking, any number of potentially adverse combinations ofmedication identified by the reader. This indication may be providedvisually, such as through use of the screen 874, audibly through use ofthe speaker 876, and/or tactilely through use of, for example, avibration device (not shown), and the like.

In one embodiment, the emission profiles 882 and associated identifyinginformation 884 are provided to the memory 868 upon manufacture of thereader 860. In another embodiment, the emission profiles 882 and theidentifying information 884 are provided to the memory 868 from astorage in a server (not shown) accessible to the reader 860 via anintegral communication module (not shown). Such communication module mayallow access to the storage by any one of a number of well known wiredor wireless communication means including Ethernet, USB, Wi-Fi (trademark), Bluetooth (trade mark), CDMA or GSM cellular technologies and thelike which the reader and server are configured to use. Updates ofreader information may be made by programmed access of the storage on aperiodic basis, or un-programmed access by a user on an as-desiredbasis. Alternately, updates may be made each time the reader 860 is usedto ensure the information 884 associated with a given emission profile882, including recommended dosage and adverse interaction data and thelike, is current.

In addition to incorporating the fragments on or in a pharmaceutical,unique rare earth doped glass fragments may be incorporated in thepackaging of pharmaceuticals. Additional benefits include more reliabledrug dispensing and administration. For example, if each drug packageincludes security markings having a PL signature unique for thefrequency and/or day or time at which the drug is to be taken, then anabsent-minded patient can use a reader to ascertain if they need to takea drug or if they have already taken the drug for that time/day. Thishas applications in a home or in a healthcare facility for theadministration of medication, and in a pharmacy for dispensingmedication, and the like.

Another example relates to the food industry. Produce, such as fruit andvegetables (but also including tins, meat, milk, yogurt, and such like),can be marked using glass particles such as the glass particles 150 in afluid medium 155 shown in FIG. 11. The glass particles may be usedinstead of, or in addition to, adhesive stickers that are currently usedon fruit. By spraying on the fluid medium, a unique glass particlehaving a unique PL signature can be applied to each type of produceitem. For example, Gala apples may have one PL signature, Macintoshapples may have another PL signature, and so on. A checkout station maybe equipped with a reader so that the produce can be automaticallyidentified and the price obtained without having to manually read anadhesive label.

Glass particles having a unique PL signature may also be used in foodproducts or additives such as, for example, peanuts. This would allow aperson who is allergic to, or intolerant of, the food product oradditive to ascertain whether the food product or additive is present ornot.

In addition, the security markers can be used to track or identifysource of a solid or liquid substance including clean and contaminatedfuels, solvents, pastes, aerosols, paints, chemicals, detergents,metals, water and such like. For example, as shown in FIG. 26, glasspowder 1000 comprising one or more billets may be added to a liquid suchas gasoline 1002 in a fuel tank 1004 at a filling station. If the fueltank 1004 subsequently develops a leak 1006, the powder 1000 can migrateto the leak and escape with the fuel 1002. A detector 1008 can then beused to excite the leaked powder 1000, detect resulting PL emission, andgenerate a PL signature which can be matched to one or morepre-determined PL signatures to identify the source and/or location ofthe leak 1006. The one or more pre-determined PL signatures may bestored in a storage 1010 associated with a remote server 1012 withinformation relating to the source (for example, the name and contactdetails of the person, whether an individual or an entity, owning,storing and/or supplying the fuel), the substance (for example, diesel)and such like. Access to the remote server 1012 may be obtained by thedetector 1008 using any one of a number of well known wirelesstechnologies such as Wi-Fi (trade mark), Bluetooth (trade mark) and GSMand/or CDMA and the like. Alternately, the remote server 1012 may beconnected to the detector 1008 via, for example, a local area network, aUSB connection and the like. Likewise, one or more of the one or morepre-determined signatures may be stored in a storage (not shown) in thedetector 1008 for directly identifying one or more particular substancesand/or their source and such like. Once determined, the identifiedsource may be contacted and appraised of the leak including, possibly,location of the leak and/or where the leaking material was detected.

Similarly, environmental pollution and unauthorized dumping of waste canbe detected and monitored by incorporating fragments of a billet into awaste material. Each large waste-producing factory may be assigned aunique PL signature, and required to incorporate glass fragments havingthat signature into all waste produced. If this waste is detected in anarea that should be free of pollution then the source of this waste canbe identified and, where appropriate, notified by a proper agency orauthority.

Likewise, this tracking function can be applied to people, animals,weapons, explosives, medical instruments, pollutants, and watercourses.It can also be applied to any article or substance generally whichmoves, and which motion is to be followed, such as blood in the humancirculatory system and food in the human digestive system.

In addition, security markers can be used to identify a component of amulti-component medium. For example, as shown in FIG. 27, a medium 1100may be manufactured using four components 1102, 1104, 1106 and 1108,where each of the four components 1102, 1104, 1106 and 1108 incorporatesa unique marker 1110, 1112, 1114 and 1116 with known, unique PLemission. A reader 1118 can then be configured to, for example, identifythe component 1106 of the medium 1100 by exciting the appropriate marker1114 and detecting the respective, unique PL emission.

As further shown in FIG. 27, the reader 1118 may comprise anillumination source 1120, a detector 1122, a processor 1124, a memory1126, a battery 1128, a switch 1130 and a display 1132. In use, thereader 1118 is activated via the switch 1130. After activation, theillumination source 1120 illuminates the medium 1100 at one or moreillumination wavelengths 1134, the one or more illumination wavelengths1134 being associated with one or more excitation wavelengths of thesecurity marker 1114 for which the reader 1118 is configured to read.Upon illumination and/or at some defined time thereafter, the detector1122 detects emission at one or more emission frequencies 1136 expectedfrom the security marker 1114 in response to the one or moreillumination wavelengths 1134. Subsequently, the processor 1124 comparesthe detected emission with one or more emission profiles 1138 stored inmemory 1126. If a match is found, this result is indicated on thedisplay 1132. If no match is found, this result is also indicated on thedisplay 1132.

Displaying the result of a match may further include displayinginformation 1140 pertaining to the matched component 1106. Theinformation 1140, which is also stored in the memory 1126, may includetrade and/or technical name, chemical composition, manufacturer,manufacturing process, manufacture date, reactivity, toxicity,mechanical properties, thermodynamic properties, and the like. Likewise,displaying the result of a non-match may further include displaying someor all of the information 1140 associated with the component 1106 forwhich the reader 1118 is configured to read, along with an indication ofits absence from the medium.

In additional embodiments, the reader 1118 may be configured tosimultaneously identify more than one of the components 1102, 1104, 1106and 1108 of the medium 1100. In such case, an indication of eachidentified component may be displayed on the display 1132, with orwithout some or all of the associated information 1140. Further, in caseno match is found, an indication of each of the components 1102, 1104,1106 and 1108 not found may be displayed on the display 1132, with orwithout the respective, associated information 1140.

In another embodiment, one or more emission profiles and any associatedinformation, including emission profile 1138 and its associatedinformation 1140, may be stored in a remote data store (not shown). Insuch case, a communication device (not shown) associated with the reader1118 may be used to download the emission profile 1138 and associatedinformation 1140 for a component 1106 to memory 1126, therebyconfiguring the reader 1118 to identify the compound 1106.

In further embodiments, the reader may be a “dumb” device whichilluminates a medium, detects resultant emission, and sends the detectedemission to a remote server via a wired or wireless communication devicefor remote processing and/or identification of one or more components.

In another aspect, security markers may be used to determine theconcentration of two or more fluids or solids in a multi-componentmedium, such as a mixture 1200 shown in FIG. 28. For example, if twodifferent composition or source fluids 1202 and 1204 are mixed, theneach fluid can incorporate glass fragments having unique PL signatures.A first set of fragments 1206 having a first PL signature can besuspended in the first fluid 1202, and a second set of fragments 1208having a second PL signature different from the first can be suspendedin the second fluid 1204. When the two fluids 1202 and 1204 arecombined, the resulting mixture 1200 will contain each of the glassfragments 1206 and 1208 in proportion to the amount of each fluid 1202and 1204 in the mixture 1200.

To determine the concentration of a component, such as the firstcomponent 1202, the mixture 1200 is illuminated, and a composite PLsignature 1220, shown in FIG. 29, is measured. The composite PLsignature 1220 reflects the contribution from the PL signatures 1222 and1224 of each of the respective fragments 1206 and 1208 in the mixture1200 of the two fluids 1202 and 1204. After detection, the composite PLsignature 1220 is processed to ascertain the contribution from the PLsignature 1222 of the glass fragments 1206 in the first component 1202.Subsequently, the concentration of the first component 1202 in themixture 1200 is calculated based on a comparison of one or more aspectsof the composite PL signature 1220 and one or more aspects of theascertained contribution of the PL signature 1222 of the glass fragments1206 in the first component 1202.

In one embodiment, the intensity of emission at a wavelength unique to agiven component is used to determine the concentration of that componentin the mixture. For example, referring to FIG. 29, the intensity ofemission I6 at wavelength λ1 is compared to the intensity of emission I1at wavelength λ1 to determine the concentration of the first component1202 in the mixture 1200.

In another embodiment, the intensity of emission at a wavelength uniqueto a given component is compared to the intensity of emission unique toone or more other components to determine the concentration of the givencomponent in the mixture. For example, referring again to FIG. 29, theintensity of emission I6 at wavelength λ1 is compared to the intensityof emission I7 at wavelength λ2 to determine the concentration of thefirst component 1202 in the mixture 1200.

In a further embodiment, the intensity of emission at a wavelengthcommon to all of the components is used to determine the concentrationof a given component in the mixture. For example, referring again toFIG. 29, the intensity of emission I5 at wavelength λ3 is compared tothe intensity of emission I6 at wavelength λ1 to determine theconcentration of the first component 1202 in the mixture 1200.

In additional embodiments, combinations of the above methods may be usedto determine the concentration of one or more components in a mixture.Likewise, the concentration of each of the components of a mixturehaving more than two components may be determined. In addition, one ormore aspects of emission including intensity, wavelength, decay time,and the like may be used to determine the concentration of eachcomponents of a multi-component mixture.

A similar identification can perform a trademark-like function, inidentifying authentic goods. Without limitation, this would apply totoner cartridges, fuels, tires, and any fungible articles in which theidentity of the manufacturer or supplier is important. One such exampleis integrated circuits. These may include a unique fragment to identifythe manufacturer, or they may include serial numbers formed fromfragments to identify the type of integrated circuit.

Security markers can also be included in ink used to tattoo people, sothat a person can use a tattoo as a secure identifier, or to gain accessto a restricted site or area.

Similarly, unique security markers can be included in military uniforms,thereby enabling identification of a soldier by the uniform that he/sheis wearing.

In the case of treating the article 210 of FIG. 13 as a human, the tag215, if exhibiting the proper PL signature, can act as an admissionpermit or key. Thus, tag 215 can grant admission to places or buildings.Or tag 215 can grant permission to use specific equipment such ascomputers and the like.

In another application, the article 210 of FIG. 13 can represent aperson or other living being. One or more glass fragments 215 on orassociated with that person or being each having a predetermined PLsignature can then be used to provide information relating to specificcharacteristics, such as color-blindness, of that person or being.

In another application, the article 210 in FIG. 13 bears no visibletags, but rather is painted with a coating containing one or more glassfragments 215 as for the article 170 in FIG. 12, wherein the coatingexhibits a predetermined PL signature when excited. Alternately, thecoating is applied only to a portion of, or in a concealed location on,the article 210.

In another application, the glass fragments can cooperate with eachother to provide information. For example, FIG. 14 illustrates a card300, upon which is superimposed an imaginary grid. Distance D ispre-established by convention. If a glass fragment is positioned withina cell 205 of the grid, that cell is treated as a logical ONE. If a cell205 is empty, that is, devoid of a glass fragment, then that cell istreated as a logical ZERO.

A reader (not shown) begins at a pre-established starting point,advances in steps of distance D, and determines whether a ONE or ZERO ispresent. A binary encoding system is thus established.

Alternately, glass fragments having two different PL signatures areused. Now the need to advance in units of D is eliminated, but can stillbe used if desired. If the two different PL signatures are A and B, thenthe sequence AABAABBB can be treated as 11011000, which is anothersystem of binary encoding.

This principle can be extended. If N types of glass fragment are used,having N different PL signatures, then an alphabet of N characters isthereby made available.

As part of the above, or any other encoding schemes, one or moreparticular PL signatures, or sequences of signatures, can be used toindicate start and/or end of an encoding sequence.

In another embodiment, the glass fragments can be used to ascertaincondition of an item, including changes thereof through abrasion, wearand such like. For example, as shown in FIG. 30 a, an item 1300comprises a laminated material having five layers, a first layer 1302, asecond layer 1304, a third layer 1306, a fourth layer 1308 and a fifthlayer 1310. Five different, rare earth doped glasses having fivedifferent, known PL signatures may be embedded in the item 1300. Glass1312 is embedded in the first layer 1302, glass 1314 is embedded in thesecond layer 1304, glass 1316 is embedded in the third layer 1306, glass1318 is embedded in the fourth layer 1308, and glass 1320 is embedded inthe fifth layer 1310.

Prior to any wear occurring, only the PL signature of the glass 1312 inthe outermost layer 1302 can be detected, presence of which indicates afirst condition of the item, namely, that the item is either unworn, oronly worn to a small extent. As shown in FIG. 30 b, after the outermostlayer 1302 is worn away, the PL signature of the glass 1314 in the nextlayer 1304 can be detected, indicating a second condition of the item,and so on. This is useful in applications where it is important todetect wear or damage to, for example, surfaces, substrates, coatings,structural members, roads, insulation, sheathing, and mechanical partssuch as wheels, tires, gears, brakes, belts, bearings, shafts, rings,fasteners and the like. Knowledge of which layer or layers are wornand/or remain can be used to identify maintenance or replacement needs.Likewise, such knowledge can individually or in the aggregate, be usedto predict wear and/or lifecycle, and therefore assist in the setting ofmaintenance and/or replacement schedules.

As shown in FIG. 31, uneven wear of an item 1330 can also be detectedif, for example, predominantly one PL signature indicative of a firstglass 1332 embedded in a first layer 1334 is present, but another PLsignature indicative of a second glass 1336 embedded in a second layer1338 is also present at one or more locations. This may provide earlywarning of wear and similarly influence maintenance and/or replacementschedule. When the glass is embedded in items such as airplane tires,this may provide a significant safety advance. In a similar way, a crackor fracture may be detected because proximate to the crack PL emissionfrom security markers embedded in lower layers may contribute to the PLsignature from the article being read. As the crack propagates, PLemission from additional layers may become evident and/or the intensityof previously identified emission may become stronger as more glass isexposed.

In another example, glass fragments may be embedded in one or more innerlayers of an item. In such case, no abrasion, wear, cracking, fractureand the like may be indicated until one or more predetermined PLsignatures associated with the embedded fragments are detected.Similarly, glass fragments may be embedded in one or more outer layers,or coatings, of an item. In such case, absence of one or morepredetermined PL signatures may be used to indicate abrasion, wear,cracking, fracture, de-lamination and the like. Likewise, presence orabsence of a predetermined PL signature, or variation in a property suchas intensity of the signature, can be used to indicate cleanliness,fouling, and such like, as well as abrasion, wear, and such like, of anitem.

These same principles can be applied to detecting whether an article hasbeen tampered with. If the security markers are arranged as a tamperevident seal, then presence or absence of a predetermined signature canbe used as evidence the seal is or has been broken.

A reader for detecting a condition of an item may be installed adjacentto the item to provide an on-line, continuous measurement of the item'scondition. Alternately or additionally, a remote and/or handheld readermay be provided for a user to measure the condition on an as-needed oras-desired basis. In addition to non-destructive evaluation of conditionof an item, such a reader can be used to assist in the non-destructiveevaluation of failure of an item.

Security markers may also be encased within an active material (“encasedmarkers”) so that when the active material is in its normal state no PLsignature is detected from the security markers. However, when theactive material reacts or otherwise appropriately changes acharacteristic, a PL signature can be recorded from the securitymarkers. The active material may, for example, change state when raisedto an elevated temperature, when melted, when worn down, when exposed toa particular atmosphere, chemical, or compound such as water, or after apredetermined amount of time has elapsed (such as a sell-by-date forfood).

Having an encased marker that is detectable when raised to apredetermined temperature is useful when the encased marker is used onfoodstuffs and food packaging that is liable to perish if raised abovethat predetermined temperature. If the encased markers are detectablewhen the temperature reaches the predetermined temperature, then anautomated system including a reader can be used to determine if the foodis at risk of perishing or becoming unsafe to consume. The encasedmarkers may be applied directly to food (for example, encased markersmay be adhered to fruit instead of an adhesive label) or to packagingfor food. Similarly, a security marker may itself change its PLsignature if its temperature is raised above a certain value. Thisallows automated reading of a security marker to ascertain if thecertain value has been reached. To achieve this temperature change,temperature dependent sensitizers may be included in the securitymarkers so that new transitions become allowed or forbidden when thecertain value of temperature is reached. Another mechanism for achievingthis is to use a host lattice that changes when the certain value oftemperature is reached. This provides an indication of quality for thefood associated with the encased marker.

In addition, security markers may be used in elections to ensure thateach voter is only allowed to vote once. This may be performed by avoter using a personal ink, as described above. Likewise, the votingpapers may include a security marker which is different for eachelection.

Security markers can also be used in a personal fluid for, for example,(i) marking possessions, or (ii) resisting attacks. In both examples,small fragments of security markers are suspended in a carrier which maybe applied as, for example, a spray such as an aerosol or mist, or aliquid through means such as brushing, dipping, pouring, and such like.

In the marking possessions example, the personal fluid may be a clearadhesive carrier 1400 in which small fragments 1402 and 1404 of securitymarkers are suspended as illustrated in FIG. 32. In such case, thefragments 1402 and 1404 could all have the same individual or collectivePL signature, which is unique to a person. To mark an item, for examplea power tool 1406, a user sprays the adhesive carrier 1400 incorporatingthe fragments 1402 and 1404 on the item using a sprayer 1408. The itemcan subsequently be identified by reading the applied carrier toascertain the PL signature of the incorporated security markers uniqueto the person.

In the resisting attacks example, the personal fluid may be a coloredink (perhaps also having a foul smell), that includes security markershaving a PL signature associated with criminal activity. If a person isattacked or a crime is perpetrated against that person, then the personcan spray the assailant with the personal spray. This will allow lawenforcement officers to track and/or identify the assailant as havingcommitted or attempting to commit a crime against the person.

Further, the security markers may be incorporated into conventionaldefensive sprays. As described above in the resisting attacks example,the security markers may include some PL signature associated with aperson, to allow law enforcement officers to associate the person withthe assailant. This can also be applied to home, store, bank, or otherprotection systems. Such a system could include a spray that sprays anyarea of the home, store or bank that is compromised by an attack so thatthe attacker and/or any object stolen or compromised would be covered bythe spray.

In another such case, security markers may be incorporated into an inkcarrier that is used to stain banknotes in the event of an attemptedtheft at a store, bank, or self-service terminal (SST) such as an ATM,and such like. Conventional banknote staining systems are sold by anumber of vendors, including Fluiditi (trade mark). Incorporation of thesecurity marker would help law enforcement officers to trace banknotesthat were stolen and stained because the stained banknotes would have aunique PL signature associated with, for example, the owner of thestore, bank, or ATM. Likewise, presence of such security markers asindicated by their PL signature may be used to manually or automaticallyreject banknotes presented to a store, bank, or SST such as an ATM, andthe like. Similarly, operation of the ATM may be disabled upon detectionof the presence of such security markers and/or proper authorities maybe automatically or otherwise notified.

In one embodiment a personal reader may be provided to a person, wherethe reader is operative to identify the PL signature of one or moresecurity markers unique to that person. Alternatively, a generic readermay be provided to one or more persons, which is operative to search adatabase to ascertain identity of a person associated with a read PLsignature. Some or all of such a database may be incorporated in amemory in the reader, or may exist in a storage in a server accessibleto the reader via one or more well known wired or wireless communicationmeans including Ethernet, USB, Wi-Fi (trade mark), Bluetooth (trademark), CDMA and GSM cellular technologies, and such like.

In all cases, a person associated with one or more security markershaving a unique PL signature may be a natural person or an artificialperson such as a corporation or other entity created by law.

Security markers may also be used to revoke a permission previouslygranted. For example, if someone has a token that includes securitymarkers having a signature that allows a user to access a restrictedarea or function, then an additional security marker (having a differentsignature) can be applied (sprayed, pressed, injected, or such like) tothe token to modify the token. When the modified token is subsequentlyread, the presence of the new PL signature can act to deny access to theuser.

Another example of the use of security markers is in the field ofguidance systems. In such use, PL signatures from luminescent securitymarkers can be assigned to correspond to, or be otherwise associatedwith, guidance information. The guidance information can compriseabsolute or relative location, direction, destination, elevation, speedlimit, topography, time to a destination, and the like. The luminescentsecurity markers can be incorporated into the surface of a roadway,railroad, curb, sidewalk, walkway, runway, step, door, deck, pavement,wall, sign, railing, floor, object, building element, and the like.Measured PL signatures of the luminescent security markers can, then,allow a pedestrian, driver, or automated vehicle, and the like to (i)manually or automatically navigate, and/or (ii) ascertain desirableguidance information such as advisory or mandatory speed limits and thelike.

One specific example involves a blind or partially sighted person 1500who has a walking stick 1502 fitted with a security marker reader 1504and a data-to-speech system 1506, as shown in FIG. 33. The surface of apavement such as a sidewalk 1508 includes a track 1510 incorporatingluminescent security markers 1512 having PL signatures associated withguidance information such as, for example, location data indicatinglocation of the pavement. In this example, as the blind person 1500walks, he or she uses the walking stick 1502 to ascertain the locationdata.

The reader 1504 includes a light source 1514 to illuminate a region ofthe sidewalk corresponding to the track 1510, a detector 1516 to detectemission from the luminescent security markers 1512 in the track inresponse to the illumination, and a processor 1518 to control thevarious components of the reader 1506. The processor 1518 also processesthe detected emission to ascertain a PL signature associated with theilluminated markers, and retrieves the associated location data using alook-up table stored in a memory 1520 in the reader 1504. The locationdata is then converted to speech and output to the blind person 1500through a speaker 1522 included in the data-to-speech system 1506.

In other embodiments, alternative sensory output including, for example,auditory, tactile, text, and/or other visual output may be included withthe stick 1502 and used to communicate the location information.Further, in another embodiment the lookup table may be stored in aremote database, access to which is obtained by the reader using any oneof a number of well known methods such as Wi-Fi (trade mark), Bluetooth(trade mark), CDMA and GSM cellular transmission, and the like. Also,additional objects, such as buildings, doors, stairs, curbs, and suchlike can also have security markers embedded in them whose PL signaturescan be used to denote their existence and location, describe theirnumber and/or size, and the like, to further aid navigation by a blindor partially sighted person.

A second specific example, shown in FIG. 34, involves a moving vehicle1530 fitted with a security marker reader 1532 aimed at a road surface1534. Security markers 1536 in the road surface 1534 have one or more PLsignatures associated with guidance information including, for example,the direction of the road, the destination of the road, the name and/ornumber of the road (for example, Interstate 70), the speed limit of theroad, and the time to a destination at the posted speed limit. As thevehicle is moving, a light source 1538 in the vehicle's security markerreader 1532 illuminates the road surface 1534 at one or moreillumination wavelengths, and a detector 1540 detects resultant emissionfrom the incorporated security markers 1536. In this case, emissionintensity and duration are detected. The detected emission intensity andduration data is processed in a processor 1542 in the reader 1532 toderive the related PL signatures, which are then used to obtain theassociated guidance information from a local data store 1544. Outputfrom the vehicle's security marker reader 1532 is conveyed to, forexample, an entertainment center 1546 within the vehicle 1530 to providean audible and visual readout to the vehicle driver 1548 and/or apassenger (not shown) of the guidance information indicated by the oneor more PL signatures of the security markers 1536 in the road surface1534, thereby allowing the driver 1548 to navigate to a desireddestination.

In one embodiment the PL signatures and associated guidance informationare loaded into the local data store 1544 upon manufacture of the reader1532. In another embodiment, the PL signatures and associated guidanceinformation are manually or automatically downloaded from a separate andpossibly remote data storage device (not shown) via any one of a numberof wired or wireless technologies on a periodic, or as-required and/oras-desired basis.

In another embodiment, an automated guidance system associated with anautomated vehicle such as a robotic delivery system for use infactories, hospitals, and such like can use information corresponding toPL signatures read from markers embedded in the floor, walls, fixtures,assembly line, and the like of a shop or hospital, to, for example,fully or partially navigate the shop or hospital.

In another embodiment, illustrated in FIG. 15, a kit 400 is provided.The kit 400 contains a number of glass beads 405. A detector 410 isprovided, such as that described in connection with FIG. 16, to detect aspecific PL signature of each of the glass beads 405. In ordinarypractice, the detector 410 will be dormant when contained within the kit400. All components of the kit 400 are contained in a common package,such as a thermo-formed blister pack 420.

The detector 410 can compare the PL signature obtained from a samplebead 405 with stored data indicating that signature. Or the detector 410can be equipped with one or more additional beads, and compare the PLsignature of one or more of those beads with the PL signature of asample bead 405.

FIG. 16 illustrates one embodiment of the detector 410 of FIG. 15. Thedetector 410 includes a disc 412, having a central hole 414, whichengages with an axle 416. The disc 412 carries a collection of glassbeads 405 each incorporating one or more rare earth dopants. The disc412 contains an indexing hole 418, which engages with an indexing pin420, allowing the detector 410 to position a desired one of the glassbeads 405 at a scanning station indicated by dashed box 422.

For example, assuming that a top side of the disc 412 is defined, thenthe beads 405 can be identified by their position (first, second, third)in the clockwise direction relative to the indexing hole 418.

Of course, the disc 412, or other carrier, may carry a single bead 405.

Scanner 410 may be controlled remotely, as by a computer 424, whichselects a specific bead 405, or sequence of beads, for scanning.

In another embodiment, additional PL signatures are added to a scannedPL signature to thwart hackers from intercepting and identifying thescanned PL signature. The additional PL signatures may be stored in andretrieved from a memory of a scanner, or computer associated with thescanner, or generated using the detector 410 shown in FIG. 16. Further,the additional PL signatures may be randomly retrieved and/or generatedto further thwart hackers.

FIG. 17 illustrates one embodiment of a sensor 500 for detectinginformation encoded in accordance with the present invention. The sensor500 includes a housing 502 in which are provided an emitter 504, forexample a light emitting diode (LED), at the output of which is provideda narrow band filter 506. The narrow band filter 506 allows only a verynarrow, pre-determined range of wavelengths to be passed. As an example,the filter could be selected to allow a narrow band centered on awavelength of 465 nm to pass through it and toward an item 508. Thesensor 500 also includes a detector 510, such as a photodiode. At itsinput is a narrow band filter 512 that allows only a very narrow,pre-determined range of wavelengths to pass through it. As an example,the filter 512 could be selected to allow light centered on a wavelengthof 615 nm to reach the detector 510.

When the sensor 500 is in use, light is emitted from the emitter 504 andpasses through the first narrow band filter 506 onto a security marker514 associated with the item 508, the security marker 514 comprising acarrier incorporating one or more rare earth dopants. A portion of thefiltered light is then absorbed by the security marker 514 which, if itmatches the energy levels of the security marker 514, causes it tophotoluminesce. PL emission from the security marker 514 then passesthrough the second filter 512 to the detector 510 for detecting presenceor absence of the filtered wavelength of light.

In another embodiment, a PL signature from a security marker associatedwith an item has multiple characteristics that can be identified. Theseinclude intensity of PL emissions at one or more wavelengths, and a timeperiod over which the emissions decay at the one or more wavelengths,among others. In the event that the PL signature has the expectedcharacteristics, the item is identified as being authentic. In the eventthat PL signature is not as expected, or one or more characteristics arenot within an acceptable range of the expected response, the item isidentified as being a potential counterfeit.

In another embodiment, multiple, different security markers, each with adifferent PL signature, are associated with an item. In such case,characteristics of the PL signature of any combination of the respectivesecurity markers, including a composite PL signature from all of therespective security markers, can be used for any of the purposesdescribed herein.

In a further embodiment, one billet of glass incorporating one or morerare earth dopants is fabricated and its PL signature is ascertained.This is repeated for numerous billets, to develop a database of dopedglasses and their PL signatures.

In one approach, every time a new billet is fabricated, its PL signatureis compared with existing signatures in the database. If the new PLsignature does not deviate sufficiently from an existing signature, thecorresponding billets are treated as interchangeable. Since the PLsignatures can, in effect, be treated as numbers, a simple formula canbe used to define similarity between the signatures. For instance, ifone PL signature has intensity I, then another PL signature having anintensity of 0.95 I can be defined as similar.

In another embodiment, no database is used. A glass foundry fabricates abillet of glass incorporating one or more rare earth dopants, ascertainsits PL signature, divides the billet into fragments, powder, or suchlike, and delivers the fragments/powder to a customer. In such case, thefoundry may include data indicating the ascertained PL signature, or thecustomer may rely on his own testing to ascertain the PL signature. Ineither case, the foundry may not retain data indicative of the PLsignature, or if it does retain such data, keep it secret.

Thus, the customer obtains a collection of rare earth doped glassfragments which, as a practical matter, are difficult to replicate. Agiven composition, producing a given PL signature, is difficult to copyto produce an identical composition which produces the same PLsignature, for several reasons. One is that the process by which thebillet is formed including heating, cooling, and heat treatment stepssuch as annealing (if any), affect its PL signature, and thoseprocessing parameters are not apparent from the composition. A secondreason is that any approach to replicate the fragments would typicallybe based on trial-and-error for which, depending on the number ofconstituents comprising the doped glass, the trials required could runinto the millions.

The spectral emissions of various marker samples have been investigated.As an example, FIG. 18 shows a table of the emission wavelengths andintensities for various different excitation wavelengths for a securitymarker comprising approximately 3 mol % EuCl₃ when included in theborosilicate glass described above. By way of comparison, FIG. 19 showsthe corresponding results for the EuCl₃:6H₂O dopant, but when insolution.

From these Figures, it can be seen that for the doped glass the mostsignificant excitation in terms of response intensity is at 395 nm, forwhich a non-dimensional intensity of PL emission is approximately 285 at615 nm. At the same excitation of 395 nm, the non-dimensional peak inemissions intensity for the EuCl₃:6H₂O is only approximately 86, andoccurs at 592.5 nm rather than the 615 nm found for the doped glass.Hence, the spectral response of the doped glass security marker at 395nm is significantly different from that of the EuCl₃:6H₂O in solution.Also when the doped glass is excited at a wavelength of 415 nm, there isa corresponding output at 590.5 nm and 615 nm. In contrast, for theEuCl₃:6H₂O in solution, there is effectively no photoluminescence atthis excitation wavelength. Again, this demonstrates that there issignificant and measurable difference caused by the incorporation of arare earth dopant in a carrier such as borosilicate glass.

Because rare earth ions have well defined and relatively narrow,non-overlapping PL emission bands, this means for many applications itis possible to detect a security marker comprising a carrierincorporating a rare earth dopant using a single, discrete,pre-determined excitation wavelength, and likewise a single, discrete,pre-determined detection wavelength. For example, for the EuCl₃ dopedborosilicate glass described above, an emitter filter could be selectedat 395 nm, and a detector filter could be at 615 nm. Alternatively, aplurality of excitation and detection wavelengths could be used. To dothis, a number of different, suitable, emitter filters could beselected, along with a plurality of corresponding detector filters. Thevarious frequency filters could be arranged as indicated by FIG. 1 toallow the simultaneous measurement of PL emissions at various differentwavelengths. It may also be beneficial to measure PL emissions atwavelengths for which no PL emission should be present to ensure that abroadband response is not being detected.

A further advantage of the discrete nature of PL emissions of rare earthions is that a number of species can be combined into the one productfor improved security. For example 3 mole % Eu can be combined with 3mole % Th, not precluding other rare earths at different percentages,and/or more than two. Because the response of the various differentdopants is relatively discrete, detection of each is simplified. Afurther advantage is that many rare earth ions are excited atwavelengths conducive to existing laser diode technologies. This makesin situ excitation possible because the excitation source is compact,robust and long-lived.

Furthermore, incorporating the rare earth dopants into a suitablecarrier, and in particular the glass beads described herein, means thatthe security marker in which the invention is embodied is extremelystable under adverse chemical, environmental and physical (e.g., wear)conditions, thereby ensuring that it has a long lifetime compared toconventional dyes.

A skilled person will appreciate that variations of the disclosedarrangements are possible without departing from the invention. Forexample, while only a few rare earth ions have been specificallydescribed, it will be appreciated that there is a wide range of PL rareearth ions that could be used. The number of permutations available istherefore greatly enhanced. In addition, while some rare earth ions emitin the UV and IR ranges, it is preferred for some applications that boththe excitation radiation and the emitted radiation are within thevisible range, which is within a wavelength range that is visible to theunaided human eye. Accordingly, the above description of a specificembodiment is made by way of example only and not for the purposes oflimitation. It will be clear to the skilled person that minormodifications may be made without significant changes to the operationdescribed. In other embodiments, other luminescent carriers may be usedthat do not rely on rare earth doping, for example carriers includingphosphorescent material, dyes, or such like; and other mechanisms forstimulation emission of radiation may be used, for example,electro-luminescence, bio-luminescence, chemi-luminescence, and suchlike.

In other embodiments, complex PL signature matching algorithms may beused to take account of errors due to rounding, and such like. Forexample, multi-dimensional vector mapping may be used, where intensitiesat multiple frequencies of interest may be represented as a singlemulti-dimensional vector. Other pattern matching techniques that couldbe applied to comparing a PL signature with pre-stored PL signatureswill be evident to those of skill in the art.

1. A method of determining a component of a medium, the methodcomprising: illuminating the medium to excite a marker associated withthe component; detecting photoluminescent emission from the marker inresponse to the excitation; comparing the detected photoluminescentemission with one or more emission profiles associated with the marker;identifying the component based on a match between the detectedphotoluminescent emission and at least one of the one or more emissionprofiles. illuminating the medium to excite a marker associated with asecond component of the medium; detecting a second photoluminescentemission from the marker associated with the second component inresponse to the excitation; comparing the detected secondphotoluminescent emission with one or more emission profiles associatedwith the second marker; and identifying the second component based on amatch between the detected second photoluminescent emission and at leastone of the one or more emission profiles associated with the secondmarker.
 2. The method of claim 1, wherein illuminating the medium toexcite a marker associated with the component comprises illuminating themedium at one or more absorption wavelengths associated with the marker.3. The method of claim 1, wherein detecting photoluminescent emissionfrom the marker comprises detecting photoluminescent emissions from themarker at one or more emission wavelengths associated with the marker.4. The method of claim 1, wherein the one or more emission profilesassociated with the marker comprise one or more photoluminescentsignatures associated with the marker.
 5. The method of claim 1, whereinthe marker comprises a carrier doped with one or more rare earthelements.
 6. The method of claim 5, wherein the carrier comprises aglass.
 7. A method of analyzing a medium comprising a plurality ofcomponents to determine a concentration of at least one of thecomponents, the method comprising: illuminating the medium to excite oneor more photoluminescent markers associated with each component of themedium; detecting photoluminescent emission from the one or morephotoluminescent markers associated with each component in response tothe excitation; generating a composite photoluminescent signature fromthe detected photoluminescent emission; processing the compositephotoluminescent signature to ascertain the contribution to thecomposite photoluminescent signature from a component; and calculatingthe concentration of the component based on the processed compositephotoluminescent signature and the ascertained contribution.
 8. Themethod of claim 7, wherein at least one of the one or morephotoluminescent markers associated with each component of the medium isunique for each component.
 9. The method of claim 7, wherein at leastone of the one or more photoluminescent markers associated with eachcomponent of the medium is the same for each component.
 10. The methodof claim 7, wherein: illuminating the medium comprises illuminating themedium at a first excitation wavelength and then illuminating the mediumat a second excitation wavelength; and detecting photoluminescentemission from the medium comprises detecting photoluminescent emissionresulting from illumination at the first excitation wavelength, thendetecting photoluminescent emission resulting from illumination at thesecond excitation wavelength.
 11. The method of claim 7, whereincalculating the concentration of the component comprises calculating aratio of intensity of photoluminescent emission from the one or morephotoluminescent markers associated with the component to a compositeintensity of photoluminescent emission from the one or morephotoluminescent markers associated with each component at one or morewavelengths.
 12. The method of claim 7, wherein the one or morephotoluminescent markers each comprise a carrier doped with one or morerare earth elements.
 13. The method of claim 12, wherein the carriercomprises a glass.
 14. A system for determining a concentration of acomponent of a medium, the system comprising: a light source whichilluminates the medium and excites one or more photoluminescent markersassociated with each component of the medium; a detector which detectsphotoluminescent emission from the one or more photoluminescent markersin response to the excitation; a processor which generates a compositephotoluminescent signature from the detected photoluminescent emission,processes the composite photoluminescent signature to ascertain acontribution from a component, and calculates the concentration of thecomponent based on the processed composite photoluminescent signatureand the ascertained contribution.
 15. The system of claim 14, whereinthe one or more photoluminescent markers each comprise a carrier dopedwith one or more rare earth elements.
 16. The system of claim 15,wherein the carrier comprises a glass.